U.S. patent application number 12/556974 was filed with the patent office on 2011-03-10 for lubricant oil compositions to optimize internal combustion engine performance.
This patent application is currently assigned to SOUTHWEST RESEARCH INSTITUTE. Invention is credited to Terrence Francis ALGER, II, Manfred AMANN, Thomas W. RYAN, III.
Application Number | 20110059878 12/556974 |
Document ID | / |
Family ID | 43648220 |
Filed Date | 2011-03-10 |
United States Patent
Application |
20110059878 |
Kind Code |
A1 |
AMANN; Manfred ; et
al. |
March 10, 2011 |
Lubricant Oil Compositions To Optimize Internal Combustion Engine
Performance
Abstract
The present disclosure relates to lubricant oil compositions
formed from base stock oils to optimize internal combustion engine
performance. Base stock oils are identified that have selected
cetane number characteristics and relatively reduced reactivity to
improve their associated combustion characteristics and reduce
engine knock without the need to modify the engine fuel or engine
parameters such as compression ratio and/or ignition timing. The
base stocks may specifically include esters of dicarboxylic acids,
esters of trimellitic anhydride and/or alklyated naphthalene
compounds.
Inventors: |
AMANN; Manfred; (San
Antonio, TX) ; ALGER, II; Terrence Francis; (San
Antonio, TX) ; RYAN, III; Thomas W.; (San Antonio,
TX) |
Assignee: |
SOUTHWEST RESEARCH
INSTITUTE
San Antonio
TX
|
Family ID: |
43648220 |
Appl. No.: |
12/556974 |
Filed: |
September 10, 2009 |
Current U.S.
Class: |
508/306 ;
508/110; 508/482; 508/496; 508/506 |
Current CPC
Class: |
C10N 2030/00 20130101;
C10M 105/06 20130101; C10M 2207/2855 20130101; C10M 2203/065
20130101; C10M 2207/2825 20130101; C10M 105/36 20130101; C10M
2207/2865 20130101; C10N 2040/255 20200501 |
Class at
Publication: |
508/306 ;
508/110; 508/506; 508/482; 508/496 |
International
Class: |
C10M 105/18 20060101
C10M105/18; C10M 169/04 20060101 C10M169/04; C10M 105/36 20060101
C10M105/36 |
Claims
1. A process for providing a reduced reactivity lubricant for
reducing engine knock in an internal combustion engine cylinder
comprising: providing a base stock oil having an IQT[Cetane
Number].sub.(-100%)(Base Stock Oil); said base stock oil formulated
for use as a lubricant for an internal combustion engine utilizing
a selected fuel having a fuel cetane number wherein IQT[Cetane
Number].sub.(-100%)(Basestock Oil).ltoreq.Fuel Cetane Number
2. The process of claim 1 wherein the IQT[Cetane
Number].sub.(-100%)(Basestock Oil) is less than or equal to 70.
3. The process of claim 1 wherein said base stock oil is further
combined in a lubricant at a concentration of at least 50% by
weight.
4. The process of claim 1 wherein said base stock oil is further
combined in a lubricant at a concentration of 75% by weight to 99%
by weight.
5. The process of claim 1 wherein the base stock oil includes
esters of dicarboxylic acids.
6. The process of claim 5 wherein the esters of dicarboxylic acids
include the reaction product of: (a) one or more of the acids
comprising phthalic acid, succinic acid, alkyl succinic acid,
alkenyl succinic acid, maleic acid, azelaic acid, suberic acid,
sebacic acid, fumaric acid, adipic acid, linoleic acid dimer,
malonic acid, alkyl malonic acid, or alkenyl malonic acid; and (b)
one or more of the alcohols comprising butyl alcohol, hexyl
alcohol, dodecyl alcohol, 2-ethylhexyl alcohol, ethylene glycol,
diethylene glycol monoether, or propylene glycol.
7. The process of claim 1 wherein the base stock oil includes
esters of trimellitic anhydride.
8. The process of claim 1 wherein said base stock oil includes an
alklyated naphthalene.
9. The process of claim 8 wherein said alkylated naphthalene
comprises one or more of the following: alpha-methylnaphthalene,
dimethylnaphthalene and/or ethylnaphthalene.
10. The process of claim 1 wherein said fuel cetane number is an
extrapolated fuel cetane number and is provided by an ignition
quality tester (IQT) where the fuel is injected into a constant
volume combustion chamber along with a solvent having a viscosity
of less than or equal to 1.0 cP at 25.degree. C. and the ignition
delay is determined as the time difference between the start of
injection and the start of combustion for different concentrations
of solvent to provide cetane numbers, wherein said fuel cetane
number is determined by linear curve fitting of a plot of said
cetane numbers versus concentration of said low viscosity solvent
excluding the 100% solvent condition.
11. A process for providing a reduced reactivity lubricant for
reducing engine knock in an internal combustion engine cylinder
comprising: providing a base stock oil having an IQT[Cetane
Number].sub.(-100%)(Base Stock Oil) wherein said base stock oil
comprises one or more of the following: (a) esters of dicarboxylic
acids; (b) esters of trimellitic anhydride; (c) alklyated
naphthalene; said base stock oil formulated for use as a lubricant
for an internal combustion engine utilizing a selected fuel wherein
said fuel provides an IQT[Cetane Number].sub.(-100%)(Fuel) and
wherein IQT[Cetane Number].sub.(-100%)(Basestock
Oil).ltoreq.IQT[Cetane Number].sub.(-100%)(Fuel).
12. The process of claim 11 wherein the IQT[Cetane
Number].sub.(-100%)(Basestock Oil) is less than or equal to 70.
13. The process of claim 11 wherein said base stock oil is further
combined in a lubricant at a concentration of at least 50% by
weight.
14. The process of claim 11 wherein said base stock oil is further
combined in a lubricant at a concentration of 75% by weight to 99%
by weight.
15. A process for identifying a lubricant for reducing engine knock
in an internal combustion engine cylinder comprising: providing a
base stock oil having an IQT[Cetane Number].sub.(-100%)(Base Stock
Oil); said base stock oil formulated for use as a lubricant for an
internal combustion engine utilizing a selected fuel having a fuel
cetane number wherein IQT[Cetane Number].sub.(-100%)(Basestock
Oil).ltoreq.Fuel Cetane Number
16. The process of claim 15 wherein: said IQT[Cetane
Number].sub.(-100%)(Base Stock Oil) comprises an extrapolated
cetane number and is provided by an ignition quality tester (IQT)
where the base stock oil is injected into a constant volume
combustion chamber along with a solvent having a viscosity of less
than or equal to 1.0 cP at 25.degree. C. and the ignition delay is
determined as the time difference between the start of injection
and the start of combustion for different concentrations of solvent
to provide cetane numbers, wherein said base stock oil cetane
number is determined by linear curve fitting of a plot of said
cetane numbers versus concentration of said low viscosity solvent
excluding the 100% solvent condition; and said fuel cetane number
is an extrapolated fuel cetane number and is provided by an
ignition quality tester (IQT) where the fuel is injected into a
constant volume combustion chamber along with a solvent having a
viscosity of less than or equal to 1.0 cP at 25.degree. C. and the
ignition delay is determined as the time difference between the
start of injection and the start of combustion for different
concentrations of solvent to provide cetane numbers, wherein said
fuel cetane number is determined by linear curve fitting of a plot
of said cetane numbers versus concentration of said low viscosity
solvent excluding the 100% solvent condition.
17. A lubricant composition for reducing engine knock in an
internal combustion engine utilizing a selected fuel wherein said
fuel has an associated cetane number, comprising: (a) a base stock
oil formulated for use as a lubricant for an internal combustion
engine wherein IQT[Cetane Number].sub.(-100%)(Basestock
Oil).ltoreq.Fuel Cetane Number (b) one or more additives combined
with said base stock oil, wherein said base stock oil is present at
a concentration such that the following applies: IQT[Cetane
Number].sub.(-100%)(Lubricant).ltoreq.Fuel Cetane Number
18. The lubricant composition of claim 17 wherein said base stock
oil is present in said lubricant at a level of at least 50% by
weight.
19. The lubricant composition of claim 17 wherein said base stock
oil is further combined in a lubricant at a concentration of 75% by
weight to 99% by weight.
20. The lubricant composition of claim 17 wherein the base stock
oil includes esters of dicarboxylic acids.
21. The lubricant composition of claim 20 wherein the esters of
dicarboxylic acids include the reaction product of: (a) one or more
of the acids comprising phthalic acid, succinic acid, alkyl
succinic acid, alkenyl succinic acid, maleic acid, azelaic acid,
suberic acid, sebacic acid, fumaric acid, adipic acid, linoleic
acid dimer, malonic acid, alkyl malonic acid, or alkenyl malonic
acid; and (b) one or more of the alcohols comprising butyl alcohol,
hexyl alcohol, dodecyl alcohol, 2-ethylhexyl alcohol, ethylene
glycol, diethylene glycol monoether, or propylene glycol.
22. The lubricant composition of claim 17 wherein the base stock
oil includes esters of trimellitic anhydride.
23. The lubricant composition of claim 17 wherein said base stock
oil includes an alklyated naphthalene.
24. The lubricant composition of claim 23 wherein said alkylated
naphthalene comprises one or more of the following:
alpha-methylnaphthalene, dimethylnaphthalene and/or
ethylnaphthalene.
Description
FIELD OF THE INVENTION
[0001] The present disclosure relates to lubricant oil compositions
to optimize internal combustion engine performance. Lubricant oil
compositions may therefore be identified, formulated and provided
to offer, for example, improved knock-resistance, fuel efficiency
and/or power generation in engines operating with gasoline or other
alternative fuel sources.
BACKGROUND
[0002] Internal combustion engine designs often seek to operate at
relatively higher power levels in an effort to improve vehicle fuel
efficiency. For example, to reduce engine displacement one may use
a pressure charging system, such as a turbocharger, to maintain the
power and torque of a relatively large engine, which may then
improve the vehicle's fuel efficiency. When a relatively smaller
engine displaces a larger engine in a given vehicle, the new
vehicle may have better fuel economy due to the reduction in
throttling losses, as a relatively smaller engine needs to open the
throttle more to achieve similar torque as in a relatively larger
engine. However, as the smaller engine may then operate at higher
power levels, the efficiency gains may be reduced by the presence
of knock. Knock is reference to the presence of detonation or
auto-ignition, resulting from relatively high temperature
conditions, which typically occur at high specific power levels,
causing auto-ignition of unburned gases in the cylinder. Knock may
produce objectionable noise and may also lead to catastrophic
engine failure.
[0003] Engine lube oil is intentionally coated on a cylinder to
reduce friction and prevent ring and liner wear. Some of this
lubricant may therefore enter the boundary layer of the cylinder
and the combustion chamber in the end gas region (the region of the
last gas to burn). It may therefore be useful to identify and
formulate lubricant compositions that may provide relatively low
reactivity and improved knock-resistance while otherwise
maintaining the lubricating efficiency of a particular lubricant
composition.
SUMMARY OF THE INVENTION
[0004] In one exemplary embodiment, the present disclosure relates
to a process for providing a reduced reactivity lubricant for
reducing engine knock in an internal combustion engine cylinder.
The process includes providing a base stock oil having an
IQT[Cetane Number].sub.(-100%)(Base Stock Oil) wherein the base
stock oil is formulated for use as a lubricant in the internal
combustion engine utilizing a selected fuel having a fuel cetane
number wherein the following relationship is observed: IQT[Cetane
Number].sub.(-100%)(Basestock Oil).ltoreq.Fuel Cetane Number.
[0005] In another exemplary embodiment the present disclosure
relates to a process for providing a reduced reactivity lubricant
for reducing engine knock in an internal combustion engine cylinder
comprising providing a base stock oil having an IQT[Cetane
Number].sub.(-100%)(Base Stock Oil) wherein the base stock oil
comprises one or more of the following: (a) esters of dicarboxylic
acids; (b) esters of trimellitic anhydride; (c) alklyated
naphthalene. Such base stock oil may then be formulated for use as
a lubricant for an internal combustion engine utilizing a selected
fuel, wherein the fuel provides an IQT[Cetane
Number].sub.(-100%)(Fuel) and wherein
IQT[Cetane Number].sub.(-100%)(Basestock Oil).ltoreq.IQT[Cetane
Number].sub.(-100%)(Fuel).
[0006] In yet another exemplary embodiment the present disclosure
relates to a process for identifying a lubricant for reducing
engine knock in an internal combustion engine cylinder comprising
providing a base stock oil having an IQT[Cetane
Number].sub.(-100%)(Base Stock Oil). The base stock oil is one that
is formulated for use as a lubricant for an internal combustion
engine utilizing a selected fuel having a fuel cetane number
wherein the following relationship is observed: IQT[Cetane
Number].sub.(-100%)(Basestock Oil).ltoreq.Fuel Cetane Number
[0007] In addition, to the above, the present disclosure is also
directed to a lubricant composition for reducing engine knock in an
internal combustion engine utilizing a selected fuel wherein said
fuel has an associated cetane number, comprising: (a) a base stock
oil formulated for use as a lubricant for an internal combustion
engine wherein the following relationship is observed: IQT[Cetane
Number].sub.(-100%)(Basestock Oil).ltoreq.Fuel Cetane Number; and
(b) one or more additives combined with the base stock oil, wherein
the base stock oil is present at a concentration such that the
following applies: IQT[Cetane
Number].sub.(-100%)(Lubricant).ltoreq.Fuel Cetane Number.
FIGURES
[0008] The above-mentioned and other features of this disclosure,
and the manner of attaining them, will become more apparent and
better understood by reference to the following description of
embodiments described herein taken in conjunction with the
accompanying drawings, wherein:
[0009] FIG. 1 is a plot of IQT derived cetane number versus %
volume of solvent (n-heptane) for Rotella T 15W-40 and Mobil Jet
Oil.
[0010] FIG. 2 is a graph of IQT derived cetane numbers for various
indicated lubricants utilizing a straight-oil measurement (no
solvent), extrapolated values (linear curve fit) including the 100%
solvent data point or IQT[Cetane Number].sub.(+100%) and
extroplated values (linear curve fit) excluding the 100% solvent
data point or IQT[Cetane Number].sub.(-100%).
[0011] FIG. 3 is a graph of IQT derived cetane numbers for the
various indicated lubricants or base stocks utilizing a
straight-oil measurement (no solvent), extrapolated values (linear
curve fit) including the 100% solvent data point or IQT[Cetane
Number].sub.(+100%) and extroplated values (linear curve fit)
excluding the 100% solvent data point or IQT[Cetane
Number].sub.(-100%).
DETAILED DESCRIPTION
[0012] The lubricant composition herein, with the aforementioned
cetane characteristics and reduced reactivity, may utilize certain
base stock oils (hydrocarbon compounds which are liquid at room
temperature) along with selected additives. The lubricant
composition may therefore be formulated to provide a particular
cetane number that, as discussed more fully below, serves to
regulate the reactivity of the lubricant to improve its associated
combustion characteristics and reduce, e.g., engine knock. In
addition, this may be accomplished without the need to modify the
engine fuel or engine parameters (e.g., compression ratio, ignition
timing, etc.).
[0013] As noted above, the combustion characteristics of a given
lubricant herein may now be evaluated and considered as a
consequence of its ability to influence the combustion process
within the cylinder of an internal combustion engine. More
specifically, by formulating a relatively low reactivity lubricant
herein with a relatively low cetane number, it has been observed
that the tendency for end-gas auto-ignition may be reduced,
allowing the engine to operate at relatively higher loads with more
advanced combustion phasing and/or higher compression ratios (e.g.,
compression ratios of greater than 10:1 to 14:1). Meanwhile,
lubricating efficiency may also be substantially preserved.
[0014] More preferably, it has been established herein that cetane
numbers for the subject lubricants or oil base stocks may be
derived from an Ignition Quality Tester (IQT) where lubricant or
base stock oil, either alone or with a selected amount of heptane,
is injected into a constant volume combustion chamber at a
temperature of about 575.degree. C. More specifically, the heated
chamber is filled with compressed air at elevated temperature.
Using a pump-line-nozzle-injector, the test lubricant may be
injected and the ignition delay may then be measured. That is, the
lubricant formulation or base stock oil combusts and the ignition
delay is determined as the time difference between the start of
injection and the start of combustion. The derived cetane number
may then be calculated using an empirical inverse relationship to
ignition delay. The IQT testing may also be checked against a
selected standard for the cetane number calculations.
[0015] Reference to a lubricant cetane number herein may be
understood as a general measure of ignition delay, i.e. the time
period between the start of injection and start of combustion
(ignition) of a given lubricant oil composition or the components
of such composition (e.g. the oil base stock). As those skilled in
the art will therefore recognize, higher cetane numbers will have
shorted ignition delay periods than lower cetane numbers. Cetane
numbers may be measured by a variety of techniques. For example,
ASTM D613 provides a cetane number of diesel fuel in terms using a
standard single cylinder, four-stroke, variable compression ratio,
indirect injected diesel engine.
[0016] However, with respect to the IQT procedures utilized herein,
it was recognized that the IQT derived cetane number was in fact
influenced by the lubricant or base stock oil viscosity (.eta.).
This may have been the case due to the fact that the IQT.TM.
procedure was originally developed for testing fuels as opposed to
the relatively higher viscosity base stock oils or lubricant
formulations. Accordingly, it was initially observed that
relatively high viscosity fluids appeared to have relatively long
ignition delay times which resulted in the observation of what was
considered to be an artificially lower cetane number. Apparently,
relatively high viscosity oils (e.g., oils with a viscosity of
greater than or equal to 3.0 cSt at 100.degree. C.) provide poor
vaporization and mixing in the IQT apparatus and therefore,
relatively delayed reaction timings. To therefore consider and
reduce the viscosity effects of the IQT screening procedures as
applied to determination of lubricant cetane numbers, the base
stock oils herein were combined with relatively low viscosity
solvents (n-heptane and iso-octane). Reference to a low viscosity
solvent therefore may be understood as solvents having a viscosity
of less than or equal to 1.0 cP at 25.degree. C.
[0017] In particular, the IQT procedure for determination and
screening of lubricant cetane numbers were developed by combining
the lubricant formulation or base stock oil with a relatively low
viscosity solvent and increasing concentrations of the oil or
lubricant for analysis, followed by extrapolation (linear curve
fitting) from the 100% solvent data point to a straight-oil
condition, or 0% solvent, which may be understood herein as
IQT[Cetane Number].sub.(+100%). In addition, linear curve fitting
was also utilized excluding the 100% solvent condition data point
which was observed to provide relatively better correlation of the
data (relatively lower extrapolated or derived cetane number). This
latter condition (exclusion of the 100% solvent condition in the
curve fitting analysis) may be understood herein as IQT[Cetane
Number].sub.(-100%). Accordingly, the base stock oils may generally
be selected herein to provide an IQT[Cetane Number].sub.(100%) of
less than or equal to 70. More preferably, the IQT[Cetane
Number].sub.(-100%) may be in the range of 1-70, including all
values therein in increments of 1.0 (e.g., 69, 68. 67, 66, etc.).
Furthermore, the IQT[Cetane Number].sub.(-100%)(Basestock Oil) may
be less than or equal to 60 or less than or equal to 50, or less
than or equal to 40, or less than or equal to 30, or less than or
equal to 20, or less than or equal to 10, or less than or equal to
5.
[0018] Moreover, the IQT[Cetane Number].sub.(-100%) of the base
stock oil is selected to be less than or equal to the IQT[Cetane
Number].sub.(-100%) of the particular fuel that may be utilized in
the subject internal combustion engine. The fuels that are
contemplated herein include gasoline as well as those alternative
fuels that are otherwise suitable for use in an internal combustion
engine, such as ethanol, natural gas, propane, hydrogen, biodiesel,
etc. For example, as gasoline may provide an IQT[Cetane
Number].sub.(-100%) of about 35, the IQT[Cetane Number].sub.(-100%)
of the base stock oil may therefore preferably be less than or
equal to 35. In other words, the base stock oils may be selected
herein to observe the following relationship:
IQT[Cetane Number].sub.(-100%)(Basestock Oil).ltoreq.IQT[Cetane
Number].sub.(-100%)(Fuel).
[0019] As may be appreciated, in the above relationship, reference
is made to the value: IQT[Cetane Number].sub.(-100%)(Fuel).
Consistent with the disclosure above, this may be understood as an
extrapolated fuel cetane number and is provided by the ignition
quality tester (IQT) where the fuel is now injected into a constant
volume combustion chamber along with a solvent having a viscosity
of less than or equal to 1.0 cP at 25.degree. C. The ignition delay
is again determined as the time difference between the start of
injection and the start of combustion for different concentrations
of solvent/fuel to provide corresponding cetane numbers, wherein
the fuel cetane number is then determined by linear curve fitting
of a plot of the determined cetane numbers versus concentration of
the low viscosity solvent excluding the 100% solvent condition.
[0020] It may be noted with respect to the above relationship, as
the fuel cetane number may be provided by other techniques, and
does not necessarily have to be determined by IQT testing protocols
alone, one may also select base stock oils such that the base stock
oil observes the relationship:
IQT[Cetane Number].sub.(-100%)(Basestock Oil).ltoreq.Fuel Cetane
Number
Accordingly, the fuel cetane number may be determined by techniques
such as ASTM D613 noted above. In addition, other references to
fuel cetane measurements include U.S. Pat. Nos. 5,475,985 and
6,609,413, the latter of which recites a method of continually
monitoring the cetane number of diesel fuels in accordance with
accepted international standards.
[0021] By way of illustration, one may conduct the above referenced
IQT procedure with the low viscosity solvent (n-heptane) followed
by the following representative test formulations: 5.0 vol % base
stock oil/95.0 vol % n-heptane; 10.0 vol % base stock oil/90.0 vol
% n-heptane; 15.0 vol % base stock oil/85 vol % n-heptane; and
25.0% base stock oil/75.0 wt % n-heptane. Reference is therefore
made to FIG. 1, which illustrates the IQT testing procedure herein
as applied to Rotella T 15-40 and Mobil Jet Oil 254. As can be seen
therein, for both samples, the IQT results for pure n-heptane
provides a cetane number of about 52. By eliminating this value for
the linear curve fitting method (indicated solid line) the IQT
cetane number was extrapolated and for Rotella T 15-40 this value
was about 77 and for Mobil Jet Oil the extrapolated value was about
36 (see also, FIG. 2). It should be noted that the curve fitting
method may be accomplished utilizing two data points (e.g., 10 vol.
% oil/90 vol. % n-heptane and 25% vol. % oil/75 vol. % n-heptane),
however, additional data points may also be utilized.
[0022] The base stock oils may preferably include an alkylated
naphthalene, which may be understood as a naphthalene compound
(C.sub.10H.sub.8) which contains one or more alkyl groups. The
alkyl groups may preferably include up to about 8 carbon atoms. For
example, the alkyl groups may include methyl, ethyl, propyl,
pentyl, hexyl, etc. The alkyl-substituted naphthalenes may
therefore include, e.g., alpha-methylnaphthalene,
dimethylnaphthalene and/or ethylnaphthalene.
[0023] Commercially available alkylated naphthalenes are available
from ExxonMobil Chemical Company under the trade name
SYNESSTIC.TM.12.
[0024] The base stock oils herein may also preferably include the
alkyl based esters of dicarboxylic acid (e.g., phthalic acid,
succinic acid, alkyl succinic acids, alkenyl succinic acids, maleic
acid, azelaic acid, suberic acid, sebacic acid, fumaric acid,
adipic acid, linoleic acid dimer, malonic acid, alkyl malonic
acids, alkenyl malonic acids, etc.) with a variety of alcohols
(e.g., butyl alcohol, hexyl alcohol, dodecyl alcohol, 2-ethylhexyl
alcohol, ethylene glycol, diethylene glycol monoether, propylene
glycol, etc.). Specific examples of these esters include dibutyl
adipate, di(2-ethylhexyl) sebacate, di-n-hexyl fumarate, dioctyl
sebacate, diisooctyl azelate, diisodecyl azelate, dioctyl
phthalate, didecyl phthalate, dieicosyl sebacate, the 2-ethylhexyl
diester of linoleic acid dimer, the complex ester formed by
reacting one mole of sebacic acid with two moles of tetraethylene
glycol and two moles of 2-ethylhexanoic acid and the like.
[0025] One particularly preferred base stock oil containing ester
functionality includes the phthalate esters, commercially available
from ExxonMobil under the name ESTEREX.TM. P81. Another suitable
base stock oil containing ester functionality includes Mobil Jet
Oil 254, which is identified as a hindered-ester base stock
formulation that includes a built-in chemical additive package.
Furthermore, another preferred base stock oil with ester
functionality includes esters of trimellitic anhydride (TMA),
otherwise known as trimellitate esters (TME). Such esters are also
commercially available from ExxonMobil under the name ESTEREX.TM.
TM101 Trimmellitate Esters.
[0026] Reference to a lubricant composition herein may be
understood as a composition that includes a base stock oil (e.g.
the alkylated naphthalene and/or ester type oils noted above) and
other appropriate additives. For example, the lubricant composition
may include the base stock oil at a concentration of at least about
50% wt., more preferably at a level of 75% wt. to 98% wt, even more
preferably at a level of 80% wt. to 98% wt. The additives may
therefore be present at a level of up to about 50% wt., more
preferably in the range of 2% wt. to 20% wt. The additives may be
selected from antioxidants, antiwear or extreme pressure compounds
(e.g. metal alkylthophosphates, sulfurized olefins, esters of
glycerols), viscosity improvers (hydrocarbons at molecular weights
of 10,000 to 1,000,000, polymers and copolymers of methacrylate,
butadiene, olefins or alkylated styrenes), detergents (alkali or
alkaline earth metal salts of sulfonates, phenates, carboxylates,
phosphates and salicylates), dispersants, pour-point depressors,
corrosion inhibitors/metal deactivators, seal-compatibility
additives, anti-foam agents, antirust additives and friction
modifiers.
[0027] Accordingly, for a given lubricant composition, which may
contain one or more of the various appropriate additives noted
above, the amount of base stock oil containing an may be selected
to provide an IQT[Cetane Number].sub.(-100%) of less than or equal
to 70. In other words, consistent with the above, the amount of
base stock oil, which is selected to itself have an IQT[Cetane
Number].sub.(-100%) of less than or equal to 70, is included in the
lubricant so that the lubricant observes a similar relationship.
That is, the lubricant herein may be selected so that it also
observes either or both of the following relationships:
IQT[Cetane Number].sub.(-100%)(Lubricant).ltoreq.Fuel Cetane
Number
IQT[Cetane Number].sub.(-100%)(Lubricant).ltoreq.IQT[Cetane
Number].sub.(-100%)(Fuel).
For example, in those situations where a particular additive may
operate to increase the reactivity of the lubricant and promote
knocking, base stock oils may now be selected herein to reduce this
tendency in the final lubricant for a given engine, taking into
consideration the type of fuel and/or a particular engine's
operating parameters that may otherwise influence engine knock.
[0028] Attention is directed to FIG. 2 which provides a graph of
the IQT derived cetane numbers for various commercially available
lubricants. The actual values of the IQT[Cetane
Number].sub.(-100%)(Lubricant) was as follows: ROTELLA T 15W-40=77;
MOBIL 15W-30=77; MOBIL Jet Oil=36; LUCAS Oil=62; VALVOLINE 2-Cycle
Oil=67; Cat NGEO SAE 40=73; PEGASUS 15W-50=80; MOBIL 1=82 and
PENZOIL ATF=80. As may therefore be appreciated, the various
commercial lubricants, except for MOBIL Jet Oil, indicated an
IQT[Cetane Number].sub.(-100%)(Lubricant) of greater than or equal
to about 70. Consistent with the disclosure here, the Mobil Jet
Oil, based on an ester base stock, indicated an IQT[Cetane
Number].sub.(-100%)(Lubricant) of less than 70, more specifically,
a value of about 36, and therefore may now be effectively screened
and selected as a candidate lubricant to reduce engine knock in an
internal combustion engine.
[0029] In addition, FIG. 2 serves to experimentally confirm what
was noted earlier, and that was the feature that the IQT screening
protocols herein, utilizing a base stock oil or lubricant in a
relatively low viscosity solvent, for IQT testing, and linear curve
fitting excluding the pure solvent data point, provides more
accurate values as opposed to IQT testing of the lubricant on its
own. As noted, it appears that the relatively high viscosity may
otherwise interfere with the IQT testing procedures, as the IQT was
originally designed for relatively low viscosity and more readily
volatized liquid fuel compositions.
[0030] Attention is next directed to FIG. 3, which compares the IQT
screening protocols herein for ROTELLA T 15W-40, MOBIL Jet Oil
(containing ester base stock), Poly-alphaolefin Basestock (PAO),
ExxonMobil SYNESSTIC.TM. 12 (alkylated naphthalenes), ExxonMobil
ESTERIX.TM. P-81 (phthalate esters) and ExxonMobil ESTEREX.TM. TME
(trimellitate esters). As noted earlier, the ROTELLA T 15W-40
indicated an IQT[Cetane Number].sub.(-100%) of about 77 and the
MOBIL Jet Oil indicated an IQT[Cetane Number].sub.(-100%) of about
36. The PAO indicated an IQT[Cetane Number].sub.(-100%) of 103. By
contrast, the alkylated naphthalene base stock indicated an
IQT[Cetane Number].sub.(-100%) of 68, the phthalate ester base
stock indicated an IQT[Cetane Number].sub.(-100%) of 47 and the
trimellitate ester base stock indicated an IQT[Cetane
Number].sub.(-100%) of 37. Accordingly, as noted and illustrated in
FIG. 3, base stocks sourced from organic esters compounds such as
phthalate esters and/or trimellitate esters and/or alkylated
naphthalenes provided IQT[Cetane Number].sub.(-100%) of less than
or equal to about 70. When such base stocks were then combined with
a lubricant additive package at levels of at least about 50% wt.,
more preferably at a level of 75% wt. to 98% wt., even more
preferably at a level of 80% wt. to 98% wt., a reduction in knock
was observed. More specifically, it was observed that there was up
to about a 10.0% increase in knock-limited torque at a fixed
compression ratio and combustion phasing and/or an improvement in
knock-limited spark advance at relatively high load conditions.
[0031] The foregoing description of several methods and embodiments
has been presented for purposes of illustration. It is not intended
to be exhaustive or to limit the claims to the precise steps and/or
forms disclosed, and obviously many modifications and variations
are possible in light of the above teaching. It is intended that
the scope of the invention be defined by the claims appended
hereto.
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